San Jose Police investigators look over the crime scene where a woman was stabbed to death in a parking lot on First street just north of Hedding Street in San Jose, Calif. on Friday, March 22, 2013. (Jim Gensheimer/Staff)

SAN JOSE -- A brazen daytime stabbing claimed the life of a 29-year-old woman Friday, setting off an intensive manhunt as the city's homicide tally for the year climbed to 10.

It happened around 2:45 p.m. in an apartment building parking lot next to a Togos sandwich shop on North First Street, near the Santa Clara County Jail and Hall of Justice on Hedding Street.

Myles Okamoto was running errands in the area when he turned onto the busy street and saw what he thought was a man beating up a woman.

"I thought it was a couple having some kind of fight," said Okamoto, 40. By then, the man already had knocked the woman to the ground but kept beating on her, savagely swinging his fists, Okamoto said. "I pulled over because I was going to do something to stop it."

But as Okamoto and others approached the pair, he saw "a lot of blood." Then he saw a blade -- the size of a butcher knife -- in the hands of the assailant, who quickly vaulted a wooden fence, leaving a bloody stain.

San Jose police spokesman Sgt. Jason Dwyer confirmed the woman was approached by a man, who stabbed her multiple time during some kind of altercation. She was pronounced dead at Valley Medical Center a half-hour later.

Dwyer said that among the passers-by and diners at the sandwich shop, numerous witnesses volunteered to give their accounts to detectives. Thus far, there's no known motive, but Dwyer said the stabbing is not believed to be gang related.

As detectives investigated the crime, cop cruisers blocked off Second Street between Hedding and Younger Avenue into the evening, and police put tape around one particular home on the block while residents gathered at either side awaiting word when they could return home.

With the assailant still on the loose, residents were advised to lock their doors and shelter in place, as was Burnett Middle School on North Second Street. San Jose Unified spokesman Paul Higgins said 240 students were on campus when the order came shortly after the stabbing, but nearly all of them had been escorted to a nearby staging area to meet parents by 5:30 p.m.

Meanwhile, the department's METRO special operations team -- wearing body armor and with police dogs in tow -- went door-to-door and through backyards but did not find the attacker.